Field of the Invention
The present invention relates to a method and apparatus for holographic display, and more particularly, to a digital holographic display method and apparatus having a small and compact structure suitable for portable electronic device.
Discussion of the Related Art
The digital holographic display is a display that reproduces phase of light waves, and expresses 3-dimensional images by modulating incident coherent light waves in order to express the phase information of light waves for an object. Since the 3-dimensional images played in a space using the holographic display provides a monocular depth recognition factor such as an accommodation effect, it is available for the holographic display to solve the accommodation-convergence mismatch that the conventional 3-dimensional display based on stereoscopy has.
The size and viewing angle of the hologram image played correlates with data capacity of spatial light modulator (SLM) which is used for modulating amplitude and phase of the incident light waves, which is spatial bandwidth representing the amount of information that optical signals have. Accordingly, the technology for expanding spatial bandwidth has been sustainably developed for increasing the size and viewing angle of a screen which is played on the digital holography.
The digital holographic display technology is considered as an ideal 3-dimensional display technology, but still has many technical problems for commercialization. One of the serious problems is extremely small size and viewing angle of the screen of the hologram played due to the narrow spatial bandwidth of the spatial light modulator. As the spatial bandwidth is proportional to the number of pixel of the spatial light modulator, the spatial bandwidth can be expanded by using multiple spatial light modulators, which is called a holographic stereogram technology. However, the holographic stereogram technology has problems such as very bulky volume due to a plurality of equipments installed for the spatial light modulator, complicated optical structures, and high cost of equipment accordingly, and so the head mounted display or the near eye display which is a display that makes the best use of the narrow spatial bandwidth is the most potential holographic display to be commercialized. However, these eyeglass-type displays have a limited utilization since there are restrictions in watching 3-dimensional images smoothly due to the shortcoming that users wear the display personally to watch the 3-dimensional images, consequently, it is required to develop a portable holographic display of glassless mode that makes the best use of the narrow spatial bandwidth.